1. Field of the Invention
The invention relates to aqueous compositions useful to make foams of limited duration and to the use of the foams to suppress coal dust.
2. Description of the Prior Art
A number of methods have been used in the past to suppress the respirable coal mine dust and so reduce the incidence of "Pneumoconiosis", more generally known as the "Black Lung" disease. A further benefit of coal dust suppression is reducing the danger of a dust explosion. The most popular current practices are (1) ventilation, (2) water spray, (3) water infusion, (4) water/wetting agent spray, (5) modified coalcutting machine design, and (6) aqueous foam application. Currently, the general practice in coal mines is a combination of ventilation and water spray. Aqueous foam application was initially studied in British coal mines. Preliminary results from a study on foam in the United States coal mines did indicate the effectiveness of this type foam in suppressing coal dust, but these developments have not yet reached the practical stage. (Kobrick, "Water as a Control Method, State-of-the-Art, Sprays and Wetting Agents," Bureau of Mines Information Circular 8458, Proceedings of the Symposium on Respirable Coal Mine Dust, Washington, D.C., November 3-4, 1969, 1970, pages 123-132). In this prior work, water plus a detergent wetting agent was used with air to foam the compositions, and as the article indicates there were certain unsolved problems to make the development practical.